Shield for radio and like apparatus



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311, N3. H. P. PRATT SHIELD FOR RADIO AND LIKE APPARATUS Original FiledAug. 7, 1926 2 Sheets-Sheet l IIAAAAAAAIAAARA!) 3 3 w a 6 3 w 7 7 WW! 34 M? 6 3 2 3 D66. 31, IQB5Q H P PRATT 2,Z6 @6@ SHIELD FOR RADIO AND LIKEAPPARATUS Original Filed Aug. '7. 1926 2 Sheets-Sheet 2 Patented Dec.31, 1935 UNITED STATES PATENT FFIQE SHIELD FOR RADEO AND LIKE APPARATUSApplication August 7, 1926, Serial No. 127,769 Renewed January 4, 193410 Claims.

My invention relates to an improvement in means for protecting the coilsand other parts of a radio set from inductive action between thedifferent pieces of apparatus and also from outside electro-magnetic andelectro-static disturbances.

It is well known that there is an inductive action between the differentpieces of radio apparatus, especially the coils of the set. Also the setis affected by electrical oscillations, as shown by the fact that manysets will respond to the radio oscillations even when the antenna isdisconnected therefrom.

There are two types of electrical forces which operate to afiect theinstrumentalities of a radio set. These disturbances may be eitherelectromagnetic or electro-static. A shield which will operate to shieldthe radio apparatus from the disturbances of one character, willoftentimes be ineffective to shield the set from disturbances of theother type.

Attempts have been made to shield the coils of a radio apparatus byproviding a thin metalic shell of copper, aluminum, or other suitablematerial, about the part to be protected. It has been found, however,that this expedient is only partially successful, as some of themagnetic lines penetrate theshell and affect the enclosed apparatusnotwithstanding. Also this expedient does not operate efficiently toshield the apparatus from the electro-static disturbances.

One of the objects of the present invention is, therefore, the provisionof means to more thoroughly protect the coils and other radio apparatusfrom electro-magnetic disturbances.

Another object of the invention is the provision of means to alsoprotect the apparatus from electro-static disturbances.

One of the features of the invention is the provision of a metalic shellor shield arranged in a magnetic field, as for instance the keeper of apermanent magnet, so that the magnetic lines of forces traverse theshell and create a magnetic shield through which the externalelectro-magnetic oscillations cannot penetrate.

Another of the features of the invention is the provision of a shield ofnon-magnetic material which may be employed, if desired, in conjunctionwith the electro-magnetic shield, just above referred to, so assatisfactorily to protect the apparatus from both electro-magnetic andelectro-static disturbances.

The electro-static shield, just referred to, may, if desired, bepositioned immediately within the electro-magnetic shield, either inintimate conaround with them; thus acting more efiiciently to protectthe apparatus within th shell.

It is believed the further disclosure of the invention will beunderstood most readily from a detailed description thereof, taken inconnection with the accompanying drawings, in

which:

Fig. 1 is a section through one form of applicants device where theshield is magnetized by means of a permanent magnet;

Fig. 2 is a similar view of a modification, in 25 which the shield ismagnetized by means of a coil mounted about the connecting leg of theU-shaped member;

Fig. 3 is a View through the coil and shield of Fig. 1 and shows therelation of the magnet 30 poles to the shield;

Fig. 4 shows another modification, in which a coil is provided about oneend of the shield, the said coil being in series with a source ofelectrical energy; 35

Fig. 5 shows a cup-shaped adjustable shield which may be moved back andforth over the coil;

Fig. 6 shows a plurality of coils, each surrounded by an individualshield, the shields be- 4 ing joined into an endless series by theconnecting tubular conduit members, preferably of magnetic material;

Fig. 7 shows a shield structure similar to that of Fig. l, but with anelectro-static shield pro- 45 vided in addition to the electro-nagnetioshield;

Fig. 8 schematically indicates a selective receiving coil structure,such as shown in applicants application, Serial No. 46,6.92, filed July29, 1925, and Fig. 9 shows a number of pieces of apparatus of a radioreceiving set each surrounded by a double shield, one a magnetic shieldand the other an electrostatic shield.

Referring now to the drawings, in which like reference charactersindicate the same parts in 55 It has been shown, however, that if 0duits.

the several views, it is a cylinder of sheet metal preferably ofmagnetic material, having the end caps or covers ll. Within the closureor shield H), II is positioned a coil or coils i2. This coil structurel2 may, if desired, comprise the usual primary and secondary and meansfor adjusting one of the coils in relation to the other. As this coilstructure is old and well known, it is not shown in detail in thepresent drawings. There is provided in connection with the shield Ii! apermanent magnet 83, between the poles M of which the cylinder ill ispositioned, as clearly disclosed in Figs. 1 and 3. The magnet i3operates to set up lines of force in the shield 59, H, which lines offorce operate in connection with the metal cylinder and end caps to forma medium through which the stray electro-magnetic lines in theatmosphere can pass with great difficulty.

Where the coil is protected merely by ashield of thin magnetic material,it is found certain of the magnetic lines will pass through this shieldand enter the coil or coils producing a disturbing effect. When,however, the shield is slightly magnetized, at least to the extent ofequalizing that of the disturbing force, these entering magnetic linesare caught by the magnetic current existing in the shield and carriedaround with it so that they may be absorbed thereby and seldom, if ever,enter the appa-' ratus within the shield. However, it is essential thatthe strength of the magnetic field within which the shield is positionedshall be properly proportioned, for if too strong the magnetic lines setup thereby may saturate and enter the shield and disturb the apparatustherein and if too weak the shielding effect above referred to will notbe sufficient to protect it.

Fig. 2 discloses an apparatus similar to that shown in Fig. 1, exceptthe magnetic lines are set up by means of the coil 55 positioned aboutthe intermediate member it of the U-shaped bar, between the ends or'poles ll of which the shield I8 is positioned. The coil l5 will bearranged in series with a suitable source of electrical energydiagramatically indicated at 89.

Fig. 4 shows another modification of applicants invention, whichconsists of the cylinder 20 having the end caps 2|, one end of thecylinder being surrounded by a coil 22 which is in series with a sourceof current indicated at 23. Theconductors 2d leading to the coil orcoils 25;within the shield 29 are provided with insulating collars Zfi,at the points where they pass through the shield 29.

Fig. 6 shows a series of shields which may be similar to that shown inFigs. 1 and 3, except that the permanent magnet is omitted. Within theshields 21, 28, 29, and 38 are pieces of radio apparatus, which in thepresent illustration, are diagramatically indicated as coils 3!. From areference to Fig. 6 it will be noted that the shields 27 and 28 arejoined by conduit 32, shields 28 and 29 are joined by conduit 33,shields 29 and 30 by conduit 34 and shields 3i! and BI by conduit 35.The conductors 35 which connect the pieces of apparatus each to theother will preferably pass through these con- About the conduits i2 and3d are arranged the coils 3! which will be wound in the same directionand arranged in series with a source of electrical energy (not shown).to be understood that the several shields shown in this figure, as wellas the conduits joining them, are preferably all of magnetic material.

It is Therefore, the coils 3T operate to set up a magnetic field, thelines of which will pass in general throughout the whole shieldstructure, operating effectively to protect the apparatus within theshield and also theconductors passing through the conduits 32 to '35,inclusive.

While in Fig. 6 a series of coils are shown within the shields 2'? to3d, inclusive, it is to be understood that other apparatus may bepositioned within these shields with beneficial efiects.

In Fig. 7 is shown a double shield comprising a magnetic shield itwithin which is an electrostatic shield il The shield it is formed ofsheet metal, preferably of magnetic material, such as described inconnection with Fig. 1 and has associated therewith a magnet, the polesof which are shown at 32. This magnet may be either a permanent magnet,as disclosed in Fig. 1, or an electro-magnet, such as disclosed in Fig.2. The inner shield will be formed from dielectric, such as glass,bakelite, or the like.

It has been found that the electro-static lines of force will oftenpenetrate the magnetic shield even though the shield is impervious tothe electro-magnetic lines, and in like manner the electro-magneticlines will pass through the electro-static shield. Therefore, in orderto protect the apparatus from both the electro-static and theelectro-magnetic lines, a double shield, similar to that shown in Fig.7, should be provided. Within the shields ii and 42 of this figure areshown a pair of coils es and 8 However, it is to be understood that anypiece of apparatus which is injuriously effected by the strayelectromagnetic or electro-static waves may be protected by a shield,such as here shown.

In Fig. 8 is shown a selective receiving coil structure composed of 3coils, each of which may be rotated. Referring to this figure, 5i!indicates a supporting stand on which the coil 5| is pivotally supportedto rotate about a vertical axis.-

The middle coil 52 is pivotally supported from the frame of coil st torotate about a horizontal axis and the innermost coil 53 is pivotallysupported on the frame of coil 52 to rotate about an axis at rightangles to the axis of rotation of coil 52. This axis, however, willchange its position as the coil 52 is rotated in respect to coil 5i.

Fig. 9 represents a series oi different radio instrumentalities, each ofwhich is enclosed by a double shield, one shield being of anelectrostatic character which may be made from nonmagnetic material, andthe other shield being of magnetic material. No magnet or other meansfor externally energizing the magnetic shield is shown in this view.This is for the reason that the coils, transformers and tubes of a radioreceiving set are capable of setting up a magnetic field in the magneticshield of their own accord which is suiiicient to overcome strayelectromagnetic influences. Within the shield 50 is diagrammaticallyillustrated a coil structure 5!, such as shown in Fig. 8. Within theshield 62 is shown a vacuum tube 63, such as disclosed in applicantsapplication No. 628,962, filed March 31, 1923. Within the shield 64 isshown a coil structure 65, which, if desired, may comprise a pluralityof coils either fixed in relation to each other, or relatively movableand within the shield 66 is shown a condenser 67 which may be of anywell known construction.

Experiments have clearly demonstrated that the several differentinstrumentalities of a radio circuit are injuriously affected by thestray electro-magnetic and electro-static waves and the system is alsoaffected by articles brought adjacent to the differentinstrumentalities. For instance, it is a common occurrence to find thatthe mere moving of the hand toward or from the equipment which iscommonly accredited to body capacity and may be likened to the dischargeof static accumulations, will change the tuning of a receiving set, andas above explained, the electrical oscillations thrown out by the piecesof apparatus themselves affected the adj acent apparatuses.

By enclosing each of the several major parts or instrumentalities of theradio apparatus in a separate shield, the equipment is almost absolutelyprotected, not only from the stray electrical oscillations arriving fromoutside sources, but also from the waves set up by the instrumentalitiesof the set. For the most delicate radio equipment it is very desirableto provide a double shield, such as shown in Figs. 7 and 9. However,with less powerful apparatus, a single shield of magnetic material maybe found sufiicient.

A shield consisting of any magnetic material may be employed withbeneficial results. However, a shield, consisting of nickel chromium andiron in parts of about sixty-five (65) per cent nickle, ten (10) percent chromium and twentyfive (25) per cent of iron, has been found togive very good results.

While in the drawings each of the radio instrumentalities is shown asprovided with a separate shield, in certain cases, a plurality ofinstrumentalities may be positioned within the same shield if insulatedfrom other instrumentalities which would injuriously affect them.

The shield partitions dividing each instrumentality from the next may becommon to adjacent instrumentailties, as for instance, where theelements are positioned within a trough like shield and the separatedevices within the member are separated from each other by partitionswhich may be either slideably inserted or fixed in position. Variousmodifications of this character will readily suggest themselves to oneskilled in the art. It is, therefore, to be understood that theapplicant contemplates many modifications and the invention, therefore,should be limited only by the scope of the appended claims.

Having thus described my invention, what I claim is new and desire tosecure by Letters Patent of the United States is.

I claim:-

1. In a radio set, an instrumentality, a magnetic shield about saidinstrumentality, said shield comprising an envelope of magnetic materialand means associated with said envelope for creating a magnetic fieldabout said envelope for magnetizing said envelope.

2. In a radio set, an instrumentality, a magnetic shield about saidinstrumentality, said shield comprising an envelope of magnetic materialand magnet poles of opposite polarity associated with and arranged onthe opposite sides of said shield to magnetize the shield.

3. In a radio set, an instrumentality, a magnetic shield about saidinstrumentality, said shield comprising an envelope of magnetic materialand a magnet for magnetizing said shield, the said envelope beingpositioned between the poles of said magnet.

4. In a radio set, an instrumentality, a shield of magnetic materialabout said instrumentality, means for creating a magnetic field tomagnetize said shield, and means for adjusting said shield relative tosaid instrumentality whereby a greater or lesser portion of saidinstrumentality is protected by said magnetized shield.

5. In a radio set, a plurality of instrumentalities and shields, saidshields being positioned about certain of said instrumentalities, eachof said shields comprising an envelope of magnetic material and meansfor creating a magnetic field about said envelope to magnetize theshield.

6. In a radio set, a plurality of instrumentalities, shields of magneticmaterial surrounding certain of said instrumentalities, respectively,conduits of magnetic material joining said shelds into a series andmeans for creating a magnetic field to magnetize said shields.

7. In a radio set, a plurality of instrumentalities, shields of magneticmaterial surrounding certain of said instrumentalities and meansassociated with the shields for creating a magnetic field within whichsaid shields are positioned for magnetizing the shields.

8. The method of protecting a radio set from foreign electricaldisturbances which consists in surrounding several of theinstrumentalities with separate shields of magnetic material andcreating a magnetic field about said shields for magnetizing theshields.

9. The method of protecting a radio instrumentality from foreignelectrical disturbances which consists in surrounding theinstrumentality with a shield of magnetic material and creating amagnetic field about said shield for magnetizing it.

10. The method of protecting a radio instrumentality from foreignelectrical disturbances which consists in substantially enclosing the instrumentality with an envelope of magnetic material and creating amagnetic field in said envelope to magnetize it.

HARRY P. PRA'I'I'.

